Apparatus for angular adjustment of camshafts relative to crankshafts in combustion engines

Abstract

An apparatus for varying the phase of the camshaft in the combustion engine of a motor vehicle has an adjuster which is connected to the camshaft and is operable to adjust the phase of the camshaft prior and subsequent to starting of the engine. To this end, the adjuster is connected with a hydraulic drive system which can operate the adjuster while the engine is idle. Once the engine is started, the drive system receives pressurized fluid from the lubricating circuit of the engine. Prior to starting of the engine, the drive system receives pressurized fluid from a source other than the lubricating circuit or from a source which is provided in addition to the lubricating circuit. The other source is preferably the hydraulic circuit of the power steering system (such as a speed-sensitive power steering system) of the motor vehicle.

What is claimed is:  
     
       1. Apparatus for adjusting the phase of a camshaft in a combustion engine which forms part of a power train in a motor vehicle and has idle and operative conditions, comprising: 
       an adjuster operatively connected with the camshaft and being operable to adjust the phase of the camshaft;  
       a fluid-operated drive means including a fluid pressurizing circuit, said circuit being arranged to build up a fluid pressure which is necessary for camshaft adjustment by said adjuster while the engine is in said idle condition;  
       a second fluid pressurizing circuit which is connected to the drive means;  
       means for establishing a path for the flow of fluid between said circuits; and  
       a pressure converter which is operable to connect the circuit of the drive means to the adjuster for regulating the flow of fluid along said path; said converter comprising:  
       a housing which defines a high-pressure chamber and a low-pressure chamber and a piston which is reciprocable in said housing between said chambers;  
       wherein the circuit of the drive means is connectable to the high-pressure chamber, and the second circuit is connectable to the low-pressure chamber.  
     
     
       2. The apparatus of claim  1 , further comprising signal generating sensor means arranged to monitor actual values of a variable parameter of the engine and being connected with said drive means. 
     
     
       3. The apparatus of claim  1 , wherein said drive means further comprises a valve including a valving element movable to a predetermined position in which the circuit of said drive means can supply pressurized fluid to said pressure converter. 
     
     
       4. The apparatus of claim  1 , wherein the motor vehicle further comprises a power steering unit including said first fluid pressurizing circuit. 
     
     
       5. The apparatus of claim  1 , wherein said regulating means comprises a membrane. 
     
     
       6. The apparatus of claim  1 , further comprising means for connecting said circuit of said drive means with said adjuster only during predetermined stages of operation of the motor vehicle. 
     
     
       7. The apparatus of claim  1 , wherein said drive means further comprises a valve operable to connect the circuit of said drive means with said second circuit. 
     
     
       8. The apparatus of claim  7 , wherein said valve comprises a four/three-way proportional valve. 
     
     
       9. The apparatus of claim  7 , further comprising a signal-transmitting engine RPM sensor connected with said valve. 
     
     
       10. The apparatus of claim  1 , wherein said, pressure converter comprises means for maintaining the pressure of fluid in the circuit of said drive means above a predetermined threshold value. 
     
     
       11. The apparatus of claim  1 , wherein said regulating means comprises a check valve arranged to permit the flow of fluid from said second circuit to the circuit of said drive means. 
     
     
       12. Apparatus for adjusting the phase of a camshaft in a combustion engine which forms part of a power train in a motor vehicle and has idle and operative conditions, comprising: 
       an adjuster operatively connected with the camshaft and being operable to adjust the phase of the camshaft;  
       a fluid-operated drive means including a fluid pressurizing circuit, said circuit being arranged to build up a fluid pressure which is necessary for camshaft adjustment by said adjuster while the engine is in said idle condition;  
       a second fluid pressurizing circuit which is connected to the drive means;  
       means for establishing a path for the flow of fluid between said circuits; and  
       a pressure converter which is operable to connect the circuit of the drive means to the adjuster for regulating the flow of fluid along said path; said converter comprising:  
       a cylinder which defines a high-pressure chamber and a low-pressure chamber and a piston which is reciprocable in said cylinder between said chambers; and  
       means for yieldably biasing the piston in a direction to expel fluid from one of the chambers;  
       wherein the circuit of the drive means is connectable to one of the chambers and the second circuit is connectable with the other of the chambers.  
     
     
       13. Apparatus for adjusting the phase of a camshaft in a combustion engine which forms part of a power train in a motor vehicle and has idle and operative conditions, comprising: 
       an adjuster operatively connected with the camshaft and being operable to adjust the phase of the camshaft;  
       a fluid-operated drive means including a fluid pressurizing circuit, said circuit being arranged to build up a fluid pressure which is necessary for camshaft adjustment by said adjuster while the engine is in said idle condition;  
       a second fluid pressurizing circuit which is connected to the drive means;  
       means for establishing a path for the flow of fluid between said circuits; and  
       a pressure converter which is operable to connect the circuit of the drive means to the adjuster for regulating the flow of fluid along said path; said converter comprising:  
       a housing which defines a high-pressure chamber and a low-pressure chamber;  
       a piston which is reciprocable in the housing between said chambers, and  
       a deformable receptacle which is received in said high-pressure chamber;  
       wherein the circuit of the drive means is connectable to the receptacle, and the second circuit is connectable to the low-pressure chamber.  
     
     
       14. Apparatus for adjusting the phase of a camshaft in a combustion engine which forms part of a power train in a motor vehicle and has idle and operative conditions, comprising: 
       an adjuster operatively connected with the camshaft and being operable to adjust the phase of the camshaft;  
       a fluid-operated drive means including a fluid pressurizing circuit, said circuit being arranged to build up a fluid pressure which is necessary for camshaft adjustment by said adjuster while the engine is in said idle condition, said circuit comprising:  
       a fluid reservoir and conduit means which defines a first path for the flow of fluid from the pressure converter to the reservoir;  
       a second fluid pressurizing circuit connected to the drive means;  
       means for establishing a second path for the flow of fluid between said circuits;  
       a pressure converter which is operable to connect the circuit of the drive means to the adjuster for regulating the flow of fluid along said second path; and  
       valve means provided in said conduit means for yieldably opposing the flow of fluid from said pressure converter to said reservoir to maintain the fluid pressure in said circuit of said drive means above a predetermined threshold value.